1. Field of the Invention
This invention relates to a photodegradable synthetic resin composition.
2. Description of the Prior Art
The quantity of synthetic resin materials used, primarily polyolefin and polystyrene resin materials, has increased tremendously in recent years because of their low cost, good moldability, stability, and resistance to degradation such as corrosion or putrefaction. Due to the stability of such resins, in recent years synthetic resin waste has begun to pose a problem of soil pollution and to damage incinerators due to the high heat generated during their incineration. Accordingly, methods for disposing of plastic wastes without causing pollution have been extensively investigated.
For example, U.S. Pat. No. 3,795,654 discloses a polyolefin film containing an oxidizing metal and a lower alkyl thiourea; U.S. Pat. No. 3,864,293 discloses a styrene resin composition containing at least one salt of an organic carboxylic acid; U.S. Pat. No. 3,888,804 discloses a composition comprising polystyrene and a photosensitizing agent represented by the formulae: ##STR1##
U.S. Pat. No. 3,903,204 discloses a process for making expandable styrene polymer particles containing a photosensitizer selected from the group consisting of xanthene, thioxanthene and their C.sub.1 -C.sub.4 alkyl derivatives.
U.S. Pat. No. 3,454,510 discloses polyolefin compositions containing a pro-oxidant and an opaquing agent, which films are suitable for forming into agricultural mulching films. The prooxidant is (a) acetyl acetonate, an alkyl acetoacetate or an alkyl benzoyl acetate of a metal, or (b) a metal stearate or oleate.
U.S. Pat. No. 3,320,695 discloses a degradable agricultural mulching film consisting of a polyolefin and an additive selected from the group consisting of unhydrogenated polyterpenes, coumarone-indene resins and rosin.
U.S. Pat. No. 3,840,512 discloses polyolefin compositions containing a free carboxylic acid and a metal salt of a carboxylic acid.
British Pat. No. 1,357,038 discloses a polymer composition comprising (a) a copolymer of styrene (for methylmethacrylate), a conjugated diene and an unsaturated ketone and (b) a thermoplastic synthetic resin other than the above-mentioned copolymer.
British Pat. No. 1,369,760 discloses an agricultural mulch comprising a polyolefin film having incorporated therein at least one additive selected from single- and multi-cation-exchanged sulfonated or wet air oxidized cokes.
British Pat. No. 1,372,830 discloses a plastic material comprising a photodegradable polyester containing ketone carbonyl groups.
British Pat. No. 1,373,707 discloses a polymer composition comprising a plastic material and one or more compounds represented by the formula: ##STR2##
British Pat. No. 1,396,238 discloses a photodegradable composition comprising (a) a polymer of a monoethylenically unsaturated hydrocarbon monomer and (b) sulfur or a dialkyl polysulfide.
The resin compositions in the above-described patents all possess photodegradability, but they are different from those of this invention.